We remember that we are talking in the future.  That's see what that apostrophe must mean.


        1.  If you take a mouse to school he'll ask you for your lunchbox.


Let's take out part of the sentence.

        1.  If you take a mouse to school ______  ask you for your lunchbox.


We know what "he" means.

    1.  If you take a mouse to school he ____ ask you for your lunch box.


What word could we put in the blank that would show we are talking in the future?
    1.  If you take a mouse to school he        ask you for your lunch box.